Convention al beverage servers in popular use have a refrigerating coil and a beverage cooling coil in a tank. The refrigerating coil makes ice and the cooling coil cools a beverage passed therethrough. A sensor is provided near the cooling coil to control the cooling temperature by controlling the rate of ice production.
For example, beer or other beverage in a barrel 37 has conventionally been served through a cock 7 into a mug or other cup after rapidly cooling from room temperature to a suitable temperature by passing through an instantaneously cooling server 33 as shown in FIG. 12. Pressure is applied on the surface of the beverage by supplying carbon dioxide gas from a carbon dioxide cylinder 34 connected to the barrel 37 through a pressure-regulating valve 35 that regulates the pressure of the carbon dioxide gas, a gas hose 36 and a fitting 39. The beverage under pressure is then sent through a down tube 38, the fitting 39 and a beverage hose 40 to a coiled beverage duct 4 in the tank 1 filled with a coolant and placed in the cooling server 33. The cooled beverage flows out when the cock 7 is opened . Reference numerals 5 and 6 designate an inlet and an outlet, respectively.
FIG. 13 shows an example of a conventional instantaneously cooling server 33 that comprises a coiled beverage duct 4 placed in a tank 1. An ice-making coil 41 cools water serving as a coolant to cool the beverage in the coiled duct 4. The ice-making coil 41 makes ice therearound during the night or other times when the server is not in use. A sensor 13 is provided to control the production of ice 12 so that the beverage in the coiled duct 4 remains unfrozen and served at a suitable temperature. Reference numerals 17, 42, 43 and 44 designate a stirrer to stir the water in the tank 1, a cooling fan, a condenser and a cooler to supply a coolant to the ice-making coil 41.
Recently cooling and refrigerating devices using electronic elements instead of fluorocarbon are finding increasing use. This technology utilizes the Peltier effect that heat other than Joule's heat is evolved and absorbed at the junction of two dissimilar conductors or semiconductors through which direct current is passed and absorption changes to evolution and vice versa when the direction of the current is reversed. The inventors developed a beverage server that cools the coolant in a tank 1 by means of a cooling unit using an electronic cooling element that is fitted to the outside of the wall of the tank 1 of the server of the type shown in FIG. 12, as proposed in Japanese Provisional Patent Publication No. 178470 of 1996.
FIG. 14 shows an example of the cooling unit just described. An electronic cooling element 8 is placed in contact with a surface (the element is attached to the bottom in the illustrated example) of a tank 1, with heat-transfer plates 31 and a heat-transfer spacer 32 placed therebetween. By the endothermic action of the Peltier effect, the cooling element 8 cools water 11, forms ice 12 in the tank 1 and cools the beverage flowing through a coiled beverage duct 4. This unit also has a sensor 13 disposed near the beverage duct 4 to control the cooling temperature by varying the current passed to the electronic cooling element 8 so that the ice is made near the duct 4 but kept out of contact therewith.
In FIG. 14, multiple electronic cooling elements 8 are provided, with heat-insulating materials 30 disposed between the individual elements. A fan 10 releases the heat absorbed by the elements 8 to the outside through a heat-release fin 9. The tank 1 is covered with a heat-insulating material 29 and an outer panel 28. Reference numerals 17 and 18 designate a water stirrer and a heat-exchange rod disposed in the coiled beverage duct 4 to make the ice 12. An electrode that becomes non-conductive when ice is formed or a temperature sensor that measures the temperature of ice is used as the sensor 13 in this server and one equipped with a refrigerating coil as described earlier.
FIGS. 15 and 16 show an example of a beverage server in which the tank 1 is cooled by an electronic cooling element attached to the side thereof. FIG. 15 is a vertical cross-sectional view and FIG. 16 is a horizontal cross-section seen in the direction of the arrow A in FIG. 15. An electronic cooling element 8 fitted to the side wall of the tank I cools water 11 that serves as a cool ant in the tank 1 and a heat-release fin 9 and a fan 10 release the generated heat. A coiled beverage duct 4 is provided in the tank 1. Beer or other beverage is supplied from an inlet 5 under pressure, cooled to a suitable temperature, and poured into a mug or other drinking cup through an outlet 6 when a pouring cock 7 is opened.
Part of the water 11 is made into ice 12 as the water 11 serving as a coolant in the tank 1 must be constantly kept cooled so that the beverage is always cooled to a suitable temperature even when served continuously. The ice 12 is formed in an area near the coiled beverage duct 4 that neither is in contact with nor extends to the inside of the coil. Thus, the beverage in the coiled duct 4 is served at a suitable temperature, i.e., between 2.degree. C. and 8.degree. C. in the case of beer, without freezing.
The contour of the ice-making zone is controlled by means of a sensor 13 placed near the beverage duct 4 and a stirrer 17 provided in the coiled duct 4 to cause the water to move therein. The sensor, such an electrode that becomes non-conductive when the ice 12 comes into contact therewith or other ordinary temperature sensor, controls the current passed to the electron cooling element 8 by sensing the boundary between the ice and water. The sensor also controls so that the beverage in the coiled duct 4 does not become over-cooled when, for example, serving is stopped.
The contour of the ice-making zone varies with the place where the sensor 13 is provided or where data for ice production control is collected. If the sensor 13 is placed on the outside of the coiled beverage duct 4 and substantially in the center of the tank 1 as shown in FIGS. 15 and 16, ice may be formed on the inside of the coiled duct as illustrated when the beverage is not poured. The ice of the illustrated shape may freeze the beverage in the coiled duct 4 or vary the temperature at which the beverage is served. An ideally shaped ice-making zone may be obtained if more elaborate control is applied by installing many sensors 13. However, complex structure and substantial cost increase are inevitable.
In the conventional beverage servers of the above-described type as shown in FIG. 13 that have an ice-making refrigerating coil in the water tank, ice 12 does not melt from the side in contact with the refrigerating coil 41 even when cooling is stopped. In the beverage servers that make ice by employing the wall of the water tank as the cooling surface as shown in FIG. 14 and FIG. 15, however, heat from the outside melts ice earlier on the cooling surface side than on the coiled beverage duct 4 side when cooling at the tank wall is stopped.
With this type of beverage servers, therefore, a deficiency of beverage cooling capacity due to ice shortage may occur after a long interruption of operation during the night or other times. On such occasions, melting may advance from the cooling surface side to, in extreme cases, a point close to the beverage cooling coil, with the sensor near the beverage cooling coil continuing to indicate that ice is present.
In the beverage server proposed in Japanese Provisional Patent Publication No. 178470 of 1996, for example, water in the tank 1 whose bottom serves as the cooling surface is cooled by the endothermic action of the electronic cooling elements 8 through the heat-transfer spacer 32 and the heat-transfer plates 31, as shown in FIG. 14. Therefore, no heat insulator is used in this cooling surface. If the sensor 13 detects the presence of ice and current supply to the electronic cooling element 8 is cut off, heat may flow into the tank through the heat-transfer plates 31 and the heat-transfer spacer 32 and, as a consequence, melting from the cooling surface side will proceed.
If cooling operation is continued without interruption to prevent the melting of ice in this type of beverage servers that employ the wall of the water tank as the cooling surface, ice will grow to the beverage cooling coil and freezes the beverage contained therein. This over-cooling can be prevented by applying a closer temperature control by detecting the water temperature distribution in the tank using many temperature sensors. However, this solution inevitably increases the cost of the server.